Pressure-controlled injector with vario-register injection nozzle

ABSTRACT

A pressure-controlled injector for injection systems for injecting fuel that is at high pressure into combustion chambers of internal combustion engines. A 3/2-way valve body is provided, which communicates with an inlet for fuel from a high-pressure collection chamber (common rail). The nozzle chamber of a nozzle needle can also be acted upon by fuel at high pressure. The stroke motion of the nozzle needle can be achieved via a hydraulic control chamber that can be pressure-relieved via a control line that has an externally actuatable control element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In injection systems for direct-injection internal combustion engines,nozzles can be used in which, depending on the stroke length of thenozzle needle in the injector body, a certain number of openings on thenozzle needle tip, which delivers the fuel that is at high pressure tothe combustion chambers, are opened or closed. Depending on the verticalposition of the nozzle needle in the injector body surrounding it, inlesser quantity a fuel that is at high pressure, depending on theopenings that are opened or closed, is injected into the combustionchamber during the preinjection phase, or a greater injection quantityis injected during the main injection phase.

2. Description of the Prior Art

In injection systems for direct-injection internal combustion engines, apreinjection phase and the ensuing main injection phase can be achievedby means of a different vertical stroke length of the nozzle needle inthe injector body surrounding it. In injection nozzles whose nozzleneedle has a number of bores or openings, some of these openings can beclosed by part of the injector body housing by means of how a partialstroke length is set, and after a total stroke of the nozzle needle hasbeen executed relative to the injector body can be opened again, so thatupon completion of the total stroke length, all the openings of thenozzle needle tip are opened, and to all these openings, fuel that is atextremely high pressure can be injected into the combustion chambers ofan internal combustion engine. Thus during the main injection phase, thenozzle needle can be brought into a vertical stroke position in whichfuel reaches the combustion chamber of an engine through all theopenings, while on the other hand a partial stroke can also beestablished in which during the preinjection phase a lesser injectionquantity is injected into the combustion chambers of the engine.

To establish the partial stroke length, a stop is required, which keepsthe nozzle needle in the injector body, in the position in the valvehousing that maintains the partial stroke, during the preinjectionphase. A stop realized by mechanical means is exposed to major stresseson material that can lead to premature wear. Premature wear of amechanical stop face means that an axial play of the nozzle needle willensue. This can lead to fluctuations in the injection quantity to beinjected into the various combustion chambers of the engine, but thisinjection quantity is defined with extreme precision in the context of apreinjection phase. Fluctuations in the fuel quantity to be injectedimpair the metering accuracy of an injection nozzle. The wear thatoccurs can also cause premature failure of the entire injection nozzleunit.

OBJECT AND SUMMARY OF THE INVENTION

With the version proposed by the invention for creating a hydraulicstop, on the one hand an essentially wear-free adjustment of a partialstroke length of the nozzle needle can be attained, and on the other, byan external opening of the control element that brings about the partialstroke position, the instant when the axial stroke length that definesthe partial stroke of the nozzle needle is cancelled can be selectedfreely.

With the externally actuatable control element provided according to theinvention, a flexible adjustment of a graduated opening of a registernozzle can be provided, so that depending on the different degree ofopening—dictated by the axial stroke position of the nozzle needle—acontrolled uncovering of the openings at the nozzle tip of the nozzleneedle can occur.

The external actuation of the control element that accomplishes anddefines the partial stroke adjustment of the nozzle needle makes itpossible to choose the instant of the partial stroke adjustment of thenozzle needle and also makes it possible to use a 3/2-way control valvefor common rail applications, on the control parts of which a verticalmotion can be impressed by way of the stressing or unstressing of anoutlet-side control part by means of an attendant pressure drop in thecontrol chamber.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be better understood and further objects andadvantages thereof will become more apparent from the ensuing detaileddescription of a preferred embodiment taken in conjunction with thedrawing, in which:

FIG. 1, the sole FIGURE of the drawing, shows the essentially verticallyaxially extending disposition of a pressure-controlled injector inlongitudinal section with a 3/2-way valve body, an externally actuatedcontrol element, a control chamber with a control piston, and a nozzleneedle extending from the control piston that has a plurality ofinjection openings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the pressure-controlled injector, positioned essentially inan elongated arrangement, which in its upper region includes a 3/2-wayvalve, a control element that can be triggered thereby, and a controlchamber with a control piston. A nozzle needle extending from thecontrol piston and having a plurality of outlet openings provided on thenozzle needle head injects the fuel, which is at high pressure, into thecombustion chamber of an internal combustion engine.

On the outlet side in the upper region of the injector 1, anactuator-actuated control valve 3 is provided in the injector housing 2.The actuator-actuatable control valve 3 can be pressure-relieved orsubjected to pressure by means of an electromagnet, to which currentmust be supplied, or a piezoelectric actuator with extremely shortresponse times. The actuator-actuated control valve, in theconfiguration shown in FIG. 1, is formed by a ball 4, which is receivedin a seat face 5. From the seat face, an outlet throttle 7 extends intoa control chamber 6. Inside the control chamber 6, into which the upperend face protrudes with the diameter d₄ of a 3/2-way control valve body,a sealing spring 8 is let in, which is braced on one end on the upperend face of the 3/2-way valve body and on the other has its abutment inan annular groove on the control chamber 6.

A supply line 11, extending from the high-pressure collection chamber(common rail)—which is not shown in further detail here—extends parallelto the line of symmetry of the injector 1 shown; with a branch 11.1, itdischarges into the valve chamber surrounding a 3/2-way control valvebody 9 and on the other, it discharges into a nozzle chamber 28, whichsurrounds the nozzle needle 29 in the lower part of the injector housing2.

The vertically movable 3/2-way control valve body 9 received in theupper part of the injector in FIG. 1 is connected in the region of thesupply line 11.1 to an inlet throttle 10 and has a tapered regionembodied with a diameter d₃ that adjoins the diameter d₄. In the regionof the diameter d₃, also identified in the drawing by reference numeral12, a release gap 13 is provided. A pressure bolt 15, which acts on atransmission element 19, is located on the underside of the 3/2-waycontrol valve body 9.

The transmission element 19 is prestressed on its underside via a spring20 and protrudes laterally past the line of symmetry of the injector 1.By means of the transmission element 19, a ball 14 acting as a sealingface can lift out of its sealing seat, or be pressed into the sealingseat by the spring element received 17 in the control element 16, inaccordance with the stroke length 18. A control line 26 dischargeslaterally into the control element 16 and extends from the controlchamber 24 of fixed rigidity disposed in the lower region of theinjector housing 2. Accordingly, the transmission element 19 isprestressed from below by the spring 20 and can be moved by the 3/2-waycontrol valve body upon actuation via the pressure bolt 15, while theball acting as a sealing face is actuatable on one side via thetransmission element 19, counter to the high pressure present in thecontrol chamber 24 via the control line 26 and counter to the sealingspring 17.

A leaking oil line 21 branches laterally off from the hollow chamberreceiving the control piston 23 and this line furthermore communicateswith a hollow chamber in the lower region of the injector housing 2, inwhich a part of the nozzle needle 29 embodied with a diameter 27 (d₂)moves vertically.

In the hollow chamber that receives the control piston 23, the upperregion of the nozzle needle 29 is shown, which extends from the controlpiston 23 through the control chamber 24 in the nozzle chamber 28, whichcan be acted upon via the supply line 11 with fuel at high pressure, asfar as the inside of the region of the injector 1 protruding into thecombustion chamber. In the control chamber 24, a sealing spring element25 acting on the control piston 23 is received, which acts on thecontrol piston 23 in such a way that by it, the nozzle needle 1 is movedback into its closing position. Branching off from the control chamber24—as already noted—is the control line 26 to the control element 16.Through the control line 26, the pressure prevailing in the controlchamber 24 also prevails in the particular hollow chamber of the controlelement 16 in which the compression spring 17 acting on the sealing face14 is received as well.

The register nozzle 30 embodied on the lower end of the nozzle needle 29is embodied with a diameter d₁, while the aforementioned middle portionof the nozzle needle 29 is embodied with a somewhat smaller diameter 27(d₂). As a result of the pressure shoulder provided in this way at thenozzle needle 29, upon an inflow of fuel at high pressure via the supplyline 11 into the nozzle chamber 28, a projection of the nozzle needle 29in the vertical direction can be attained, counter to the compressionspring 25 received in the control chamber 24. A first injection shoulder31, for instance for performing a preinjection at a partial strokeposition of the nozzle needle 29, and a second pair of injectionopenings inside a second injection shoulder 32 are shown schematicallyhere at the head of the register nozzle 30. Upon a projection motion ofthe register nozzle head 30 out of the register head that surrounds itin the state shown, the injection quantity, for instance in the contextof a preinjection phase, accordingly first exits from the openings inthe first injection nozzle into the combustion chamber of the engine. Ifthe register nozzle 30 is projected farther out of the valve housing 2,the openings of both injection shoulders 31 and 32 protrude into thecombustion chamber of an internal combustion engine. For the sake ofcompleteness, it should be noted that reference numeral 33 indicates theopening of the injector housing 2 into the combustion chamber of aninternal combustion engine.

The aforementioned diameter graduation between the diameter 27 in themiddle region of the nozzle needle 29 and the diameter d₁ of theregister nozzle creates a pressure shoulder that upon action on thenozzle chamber 28 by fuel at high pressure emerging from thehigh-pressure collection chamber through the supply line 11 effects aprojection of the register nozzle 30 into the combustion chamber and aninjection of fuel. As a result, the control piston secured to the upperregion of the nozzle needle 29 moves part way into the control chamber24, and as a result braking of the projection motion of the nozzleneedle out of the injector housing 2 occurs. A slight pressure increasein the control chamber 24 is associated with the projection motion ofthe control piston 23 out of its guidance into the control chamber, andthis pressure increase acts on the control element 16 via the controlline 26. As a result, the register nozzle 30 is retained in a verticalposition, which corresponds to a partial stroke in the axial direction.This partial stroke position and the resultant projection motion of thefirst injection shoulder into the combustion chamber of an engine ismaintained until such time as the pressure in the control chamber 24 isnot relieved by the control element 16. If conversely a pressure reliefof the control chamber 24 takes place by opening of the control element16 by the uncovering of its seat face 14 by externally actuatedtriggering of the 3/2-way valve body via the control part 3 provided onthe outlet side, then the nozzle needle 29 moves all the way out of theinjector housing 2, which tapers to a sharp point, and as a result bothinjection shoulders 31 and 32 protrude into the combustion chamber ofthe engine, and in the context of a main injection phase, for instance,a greater quantity of fuel that is at high pressure can be injected intothe combustion chamber.

The external actuation, that is, the opening of the sealing face 14 andthe control element 16, accordingly takes place by a vertical motion ofthe 3/2-way control valve body 9 and its bore in the injector housing 2,by means of an electromagnetically effected pressure relief of the ball4 and thus a pressure relief of the control chamber 6, or via atriggering of a piezoelectric actuator, which has an extremely shortresponse time. This assures that by the disposition of a pressure bolt15, the vertical motion of the 3/2-way valve let, body 9 upon pressurerelief of the control chamber is transmitted to the transmission element19, which in turn assures an uncovering of the sealing face 14 in thecontrol element 16, and as a result the pressure prevailing in thecontrol chamber 24 is relieved. The pressure prevailing in the controlchamber 24 reinforces the force that is exerted on the control piston 23by the sealing spring element provided in the control chamber 24.

Because of the external actuation of the control element 16, which canbe embodied for instance as a trigger valve, the instant of pressurerelief of the control chamber 24 can be established and preselected,freely and independently of the pressure level prevailing in thehigh-pressure supply line 11 and 11.1, at which the control element 16,by opening of the control element 16 with the sealing face 14 via thetransmission element 19 pressure-relieves the control chamber 24. Thusthe instant of pressure relief of the control chamber 24 can bedetermined freely, and as a result the instant between a preinjectionphase and a main injection phase can be determined.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

I claim:
 1. A pressure-controlled injector for injection systems, forinjecting fuel that is at high pressure into combustion chambers ofinternal combustion engines, the injector having a 3/2-way valve body(9), having an inlet (11), which communicates with a high-pressurecollection chamber for fuel that is at high pressure, and having anozzle needle (29) whose nozzle chamber (28) can also be acted upon byfuel that is at high pressure, the improvement comprising a hydraulicchamber (24) with an externally actuatable control element (16), whichchamber controls the stroke motion of the nozzle needle (29), can bepressure-relieved, wherein the 3/2-way valve (9) is actuatableindependently of the control element (16).
 2. The pressure-controlledinjector of claim 1, wherein said 3/2-way valve (9) is disposed in theupper region of the injector (1) and actuates a prestressed transmissionelement (19).
 3. The pressure-controlled injector of claim 2, whereinsaid transmission element (19) opens and closes said control element(16).
 4. The pressure-controlled injector of claim 1, wherein pressurein said hydraulic control chamber (24) is present at the control element(16) via a control line (26).
 5. The pressure-controlled injector ofclaim 1, wherein a nozzle chamber (28) and the 3/2-way valve body (9)communicate with the supply line (11) from the high-pressure collectionchamber (common rail).
 6. The pressure-controlled injector of claim 1,wherein the diameter (27) d₂ of the nozzle needle (29) is dimensioned tobe less than the diameter d₁ of the register nozzle (30), and as aresult a pressure shoulder is created.
 7. The pressure-controlledinjector of claim 4, wherein the pressure present in the hydrauliccontrol chamber (24) fixes the nozzle needle (29) and, when a sealingface (14) at the control element (16) is closed, fixes the strokeposition of the nozzle needle (29) in the partial stroke position. 8.The pressure-controlled injector of claim 1, wherein said 3/2-waycontrol valve that can be acted upon by the fuel that is at highpressure is actuatable by means of an actuator-actuated control part(3), associated with it, on the outlet side.
 9. The pressure-controlledinjector of claim 1, wherein said the 3/2-way valve body (9) and thecontrol chamber (28) of the nozzle needle (29) communicate jointly withthe supply line (11, 11.1) from the high-pressure collection chamber(common rail) but are controllable independently of one another.